Reproduction of issue 5141 for Mocha

To reproduce:

# Either do this (*do not* run npm install!)
npx mocha
# Or this
node /path/to/mocha/bin/mocha.js

Expected behaviour:

Error: Unable to parse /home/dhd/work/flair/src/mocha-5141/package.json: SyntaxError: Expected double-quoted property name in JSON at position 570

Actual behaviour:

Error: No test files found: "test"

Note that if you run mocha from npm, (i.e. via a "test" script in package.json), then npm will catch the invalid JSON. Running mocha directly ought to do this too (since if your package.json is invalid, you already have problems).